Bioburden Testing and Sterility Testing

Producing safe products is a core goal of all medical device manufacturers and sterility assurance is a key component in achieving that goal.  Many single use medical devices are terminally sterilized by ethylene oxide or radiation methods such as gamma or e-beam.  The FDA and other regulatory bodies requires that the sterilization process be validated and these validations typically require a bioburden and sterility testing.  Sterility testing and bioburden testing are also performed on devices as part of routine quality control.

Bioburden Testing of Medical Devices

A bioburden test determines how many microbes are on the medical device.  Before performing the test, a suitability test must first be performed.   The purpose of the bioburden suitability test is to ensure that the bioburden test method is effective in recovering microorganisms that are present on the device and to show that the test method does not inhibit growth of the recovered microorganisms.  To perform the test, a known number of microorganisms are placed on a sterile device and then removed using the same method that would be used for the actual bioburden test.  If the bioburden test method was not able to remove a significant portion of the microorganisms on the device then the sterilization cycle or dose may be inadequate.  Based on the outcome of the suitability test, a recovery factor is determined to account for the percentage of microorganisms that were not able to be removed from the device.

After the suitability test is complete, the device will undergo bioburden testing to determine their microbiological load. This device bioburden level is often used in sterilization validations to calculate the dose or sterilization time a device may need. Additionally, as part of quality control, quarterly bioburden testing is done to determine whether the microbiological load on a device has changed.

Sterility Testing of Medical Devices

When performing a sterility test, it is imperative that the lab is testing that the device is actually sterile rather than leaching out chemicals that could impair the growth, or even kill, microorganisms.  Therefore, just like bioburden testing, sterility testing also has a suitability test.  The sterility suitability test is called bacteriostasis and fungistasis testing. A bacteriostasis and fungistasis test measures whether a device inhibits the growth of bacteria or fungi, which may lead to false negatives during sterility testing.  The test is performed by adding the device to media and then inoculating the media with less than 100 CFU of three different organisms.  If the three organisms are able to turn the media turbid, the device passes the suitability test and sterility testing can begin.

Sterility testing of medical devices are typically performed using media called SCDM (Soybean-Casein Digest Medium).  The device is physically placed in the media.  The amount of sample required depends on the testing method chosen, but all methods require an incubation time of fourteen days.  If the media has turned turbid after fourteen days, the sample has failed the sterility test.

ISO 11137 Dose Audits

Quarterly dose audits are performed according to ANSI/AAMI/ISO 11137 and are done as a check to ensure that the sterilization process is still producing adequately sterilized products. All sterility testing is conducted in an ISO Class 5 environment.

The microbiology lab at Pacific BioLabs is experienced in preparing and testing a wide variety of devices, from small needles to large, complex devices. For large devices, Sample Item Portion (SIP) preparation may be necessary. This consists of cutting a device into pieces for testing, or selecting the most appropriate parts of a device for testing.

Bioburden and Sterility Testing Services

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